JP5323585B2 - Induction heating apparatus, fixing apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to an induction heating device, a fixing device, and an image forming apparatus, and more particularly to control of a high-frequency current supplied to an exciting coil that heats a heat roller of the fixing device by electromagnetic induction.

  2. Description of the Related Art Conventionally, there has been proposed an image forming apparatus including a fixing device that supplies a high-frequency current to an excitation coil provided in a heat roller of a fixing device and performs electromagnetic induction heating using the excitation coil as a heat source. The fixing device and the image forming apparatus that perform such electromagnetic induction heating may cause flickering in other lighting devices due to the electric power that is rapidly consumed at the start of electromagnetic induction heating. Therefore, in the fixing device and the image forming apparatus that perform the electromagnetic induction heating, as shown in Patent Document 1 below, the amount of change per unit time of the high-frequency power supplied to the heat roller of the fixing device at the start of electromagnetic induction heating is calculated. A technique has been adopted in which the power consumption at the start of electromagnetic induction heating is kept constant and flicker phenomenon occurring in other lighting devices and the like is suppressed.

JP 2004-37868 A

  However, in the case of the conventional fixing device and the image forming apparatus, in order to suppress the flicker phenomenon, it is still necessary to suppress the power consumption at the start of electromagnetic induction heating. For this reason, it has not been improved that the power supplied from the induction heating device for heating the heat roller takes time to rise up to the target power required for heating the heat roller. No measures are taken.

  The present invention has been made to solve the above-described problem, and while suppressing the flicker phenomenon, the electromagnetic induction heating power is raised to a target power required for heating the heat roller in a shorter time than before. For the purpose.

The invention according to claim 1 of the present invention comprises an exciting coil for heating a heat roller by electromagnetic induction,
A current supply controller for controlling the supply of high-frequency current to the exciting coil;
From the start of the supply of the high-frequency current to the excitation coil until the value of the power supplied to the excitation coil reaches a predetermined power value that is assumed not to cause flickering in other lighting devices . In the first period, the frequency per unit time of the high-frequency current is increased and the frequency is continuously decreased, and the value of power supplied to the exciting coil reaches the predetermined power value. In the second period from the point in time until reaching a predetermined target power that can be used for heating the heat roller, the amount of decrease in the frequency of the high-frequency current per unit time is less than the amount of decrease in the first period. The induction heating apparatus includes a frequency changing unit that continuously reduces the frequency and lowers the frequency, and changes the frequency of the high-frequency current set by the current supply control unit.

  In the present invention, the first period from when the frequency changing unit starts supplying the high-frequency current to the exciting coil until the value of the power supplied to the exciting coil reaches a predetermined power value is A second period from when the value of power supplied to the excitation coil reaches the predetermined power value until the frequency reaches the predetermined target power by increasing the frequency per unit time. Changes the frequency of the high-frequency current set by the current supply control unit by making the frequency-frequency reduction per unit time smaller than that of the first period. Here, the influence of the flicker phenomenon is small when the power supplied to the exciting coil is low. In the present invention, the value of the power supplied to the exciting coil is determined in advance from the first period when the power supplied to the exciting coil is relatively low (from the start of the supply of the high-frequency current to the exciting coil. The frequency change unit increases the amount of increase in power per unit time by increasing the frequency per unit time reduction in the frequency of the high-frequency current during the period until the power value is reached). However, it is possible to greatly increase the power used for heating the object to be heated.

  Therefore, according to the present invention, it is possible to start up the electric power for electromagnetic induction heating to the target electric power required for heating the heated object in a shorter time than before while suppressing the flicker phenomenon. Moreover, it becomes possible to raise a to-be-heated body to target temperature more rapidly than before. Further, the total power for raising the heat roller to the target temperature can be reduced.

The invention according to claim 2 is the induction heating device according to claim 1,
A voltage detection unit for detecting a power supply voltage supplied to the excitation coil;
A temperature detection unit for detecting the temperature of the heat roller ;
The frequency change unit stores a plurality of frequency change patterns indicating patterns of a decrease width of the high-frequency current frequency in the first and second periods, and is detected by the voltage detection unit immediately before the start of high-frequency current supply A frequency change pattern corresponding to the power supply voltage and the temperature of the heat roller detected by the temperature detection unit is selected from the plurality of frequency change patterns, and the current supply control unit according to the selected frequency change pattern. The frequency of the set high-frequency current is changed.

  According to this invention, the frequency changing unit lowers the frequency of the high-frequency current in the first and second periods according to the power supply voltage supplied to the exciting coil immediately before the start of high-frequency current supply and the temperature of the heated object. A frequency change pattern that is a width pattern is selected, and the frequency of the high-frequency current set by the current supply control unit is changed in accordance with the selected frequency change pattern. It becomes possible to appropriately change the frequency of the high-frequency current in the two periods. Therefore, according to the present invention, it is possible to more efficiently realize both suppression of the flicker phenomenon and shortening of the startup time to the target power of the electromagnetic induction heating power. Furthermore, in order to start the fixing device by changing the high-frequency current by changing the frequency according to a predetermined frequency change pattern to heat the object to be heated and changing the high-frequency current with a simple configuration and a predetermined configuration Control can be performed.

The invention according to claim 3 is the induction heating device according to claim 1 or 2,
A heat roller that will be heated by the induction heating device, and a pressure roller which is brought into contact with the heat roller, a fixing for fixing the formed on a recording medium an image on the recording medium by the heat roller and the pressure roller A fixing device.

The invention according to claim 4 is an induction heating apparatus according to claim 1 or 2,
An image forming unit that forms an image based on image data on a recording medium;
A heat roller that will be heated by the induction heating device, and a pressure roller which is brought into contact with the heat roller, a fixing for fixing the formed on a recording medium an image on the recording medium by the heat roller and the pressure roller And an image forming apparatus.

  According to these inventions, the same effect as that of the invention described in claim 1 or claim 2 can be obtained.

  According to the present invention, the electric power for electromagnetic induction heating can be raised to the target electric power required for heating the heat roller in a shorter time than before while suppressing the flicker phenomenon.

1 is a side view schematically showing an internal configuration of an image forming apparatus according to an embodiment of the present invention. It is a block diagram for explaining an operation function of a fixing device, an induction heating device, and a main body side control unit that controls the fixing device. It is a figure which shows the example of the several frequency change pattern memorize | stored in the frequency change pattern memory | storage part with a graph. It is a figure which compares the frequency change pattern of this embodiment with a graph compared with the conventional frequency change pattern. It is a figure which shows the change of the electric energy at the time of changing the frequency of a high frequency current according to the said frequency change pattern with a graph. 6 is a flowchart showing frequency control of a high-frequency current by an IH control unit during a fixing operation by a fixing device.

  Hereinafter, embodiments of an induction heating device, a fixing device, and an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a side view schematically showing an internal configuration of an image forming apparatus 1 according to an embodiment of the present disclosure. The image forming apparatus 1 may be a copying machine, a printer, a facsimile machine, or the like, and may be any image forming apparatus having a process for fixing a toner image placed on a sheet by pressing and heating. The image forming apparatus 1 includes a main body unit 2, a stack tray 3 disposed on the left side of the main body unit 2, a document reading unit 4 disposed on the top of the main body unit 2, and a document reading unit 4. A document feeder 5 is provided.

  An input operation unit 6 is provided on the front part of the image forming apparatus 1. The input operation unit 6 displays a power key, a start key for a user to input a print execution instruction, a numeric keypad for inputting the number of copies to be printed, operation guide information for various copying operations, and the like. For example, the display unit 9 includes a liquid crystal display having a touch panel function.

  The document reading unit 4 includes an image sensor such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) and a scanner unit 13 including an exposure lamp, a document table 14 formed of a transparent member such as glass, and a document reading slit. 15. The scanner unit 13 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 14, the scanner unit 13 is moved along the document surface at a position facing the document table 14, and the document image is displayed. Image data acquired while scanning is output to an image memory (not shown). When reading the document fed by the document feeding unit 5, the document is moved to a position facing the document reading slit 15 and synchronized with the document feeding operation by the document feeding unit 5 via the document reading slit 15. The image of the original is acquired and the image data is output to the image memory.

  The document feeder 5 includes a document placement unit 16 for placing a document, a document discharge unit 17 for discharging a document whose image has been read, and one document placed on the document placement unit 16. A document transport mechanism 18 including a paper feed roller, a transport roller (not shown), and the like for feeding the paper one by one to a position facing the document reading slit 15 and discharging it to the document discharge section 17 is provided.

  Further, the document feeding unit 5 is provided so as to be rotatable with respect to the main body unit 2 so that the front side thereof can move upward. By moving the front side of the document feeder 5 upward to open the upper surface of the document table 14, the user can place a read document, for example, a book in a spread state, on the upper surface of the document table 14. ing.

  The main body 2 includes a plurality of paper feed cassettes 19, a paper feed roller 20 that feeds the paper from the paper feed cassette 19 one by one and transports it to the image forming unit 21, and an image on the paper transported from the paper feed cassette 19. And an image forming unit 21 for forming the image.

  The image forming unit 21 outputs a laser beam or the like based on the image data acquired by the scanner unit 13 to expose the photosensitive drum 22, and forms an electrostatic latent image on the surface of the photosensitive drum 22. A developing unit 24 that forms a toner image by attaching toner to the surface of the photosensitive drum 22 on which the electrostatic latent image is formed; and a transfer unit 25 that transfers the toner image on the photosensitive drum 22 to a sheet. Prepare.

  The fixing device 28 includes a heat roller 26 and a pressure roller 27 that heat the paper on which the toner image is transferred to melt and fix the toner image on the paper.

  In the paper conveyance path in the image forming unit 21, conveyance roller pairs 30 and 31 that convey the paper to the stack tray 3 or the discharge tray 29 are provided.

  When images are formed on both sides of a sheet, after the image is formed on one side of the sheet by the image forming unit 21, the sheet is nipped between the pair of transport rollers 30 and 31 on the discharge tray 29 side. To do. In this state, the conveyance roller pairs 30 and 31 are reversed to switch back the paper, and the conveyance roller pairs 38 and 39 send the paper to the paper conveyance path 32 and convey it again to the upstream area of the image forming unit 21. After the image is formed on the other side by 21, the paper is discharged to the stack tray 3 or the discharge tray 29.

  FIG. 2 is a block diagram for explaining the operation functions of the fixing device 28, the induction heating device 10, and the main body side control unit 51 that controls the fixing device 28. The main body side control unit 51 is configured by a CPU (Central Processing Unit) or the like, reads a program in accordance with an instruction signal or the like input from each component of the image forming apparatus 1, and executes processing. The image forming apparatus 1 is comprehensively controlled by outputting an instruction signal to the functional unit.

  Further, the main body side control unit 51 is provided in the main body unit 2, and a current that stops the supply of a high frequency current to the excitation coil 43 by the drive circuit 42 and a fixing instruction signal that causes the fixing device 28 to perform a fixing operation during image formation. The cutoff instruction signal is output to the IH control unit 41, and the IH control unit 41 is controlled for the fixing operation.

  The fixing device 28 includes a heat roller 26, a pressure roller 27 (not shown in FIG. 2), an IH control unit 41, a drive circuit 42, an excitation coil 43, a temperature sensor 44, and a voltage detection unit 45. The induction heating device 10 includes an IH control unit 41, a drive circuit 42, an excitation coil 43, a temperature sensor 44, and a voltage detection unit 45. It should be noted that a portion of the induction heating device 10 excluding the exciting coil 43 may be provided in the main body 2 of the image forming apparatus 1 separately from the fixing device 28.

  The exciting coil 43 is provided inside a cylindrical heat roller 26 made of a conductive material.

  The temperature sensor 44 is a sensor that detects the surface temperature of the heat roller 26. The temperature sensor 44 outputs the detected surface temperature to the main body side control unit 51 and the IH control unit 41.

  The voltage detector 45 detects the power supply voltage supplied to the exciting coil 43 in the heat roller 26 and outputs the detected voltage value to the IH controller 41.

  The drive circuit (current supply control unit) 42 is driven by the control of the IH control unit 41 and supplies a high-frequency current to the excitation coil 43. An induced eddy current is generated in the main body of the heat roller 26 made of a conductive material by the high frequency magnetic field generated in the exciting coil 43 by this current supply, and the heat roller 26 generates heat.

  The IH control unit (frequency changing unit) 41 is configured by a CPU or the like, and controls the drive circuit 42 according to the instruction signal output from the main body side control unit 51. Specifically, when the IH control unit 41 heats the heat roller 26 based on the fixing instruction signal output from the main body side control unit 51, the IH control unit 41 sets the detected temperature value by the temperature sensor 44 and the detected voltage value by the voltage detection unit 45. Based on this, the frequency of the high-frequency current supplied to the exciting coil 43 is calculated and output to the drive circuit 42. Further, when a current interruption instruction signal is output from the main body side control unit 51, the IH control unit 41 performs current interruption control on the drive circuit 42. By this current interruption control, the drive circuit 42 stops the supply of the high frequency current to the exciting coil 43.

  The IH control unit 41 includes a frequency change pattern storage unit 411. The frequency change pattern storage unit 411 includes a memory such as a ROM, and stores a plurality of frequency change patterns which are frequency patterns to be changed with time. The frequency change pattern corresponds to the high-frequency current during a period from the start of the supply of the high-frequency current to the heat roller 26 by the drive circuit 42 until the value of the power supplied to the heat roller 26 reaches a predetermined target power. This is a frequency pattern of the high-frequency current that is changed by the IH control unit 41 with the passage of time from the start of current supply.

  The frequency change pattern storage unit 411 stores a plurality of frequency change patterns prepared according to the surface temperature t of the heat roller 26 immediately before the start of supply of the high frequency current and the power supply voltage value v supplied to the heat roller 26. . FIG. 3 is a graph showing an example of the plurality of frequency change patterns. In FIG. 3, as an example, the frequency change pattern used when the surface temperature t is 50 ° C. and the power supply voltage value v is 120 (V) is indicated by a broken line, and the surface temperature t is 50 ° C. and the power supply voltage value v is 100 ( The frequency change pattern used in the case of V) is shown by a solid line, and the frequency change pattern used when the surface temperature t is 150 ° C. and the power supply voltage value v is 100 (V) is shown by a one-dot chain line. However, it is not intended to limit the number of frequency change patterns stored in the frequency change pattern storage unit 412 to three. Many frequency change patterns are stored in the frequency change pattern storage unit 412 so as to correspond to the surface temperature t of the heat roller 26 and the power supply voltage value v supplied to the heat roller 26 immediately before the start of supply of various high-frequency currents. It is preferable.

  In the frequency change patterns of the present embodiment, the value of the power supplied to the heat roller 26 from the start of the supply of the high-frequency current to the heat roller 26 is a predetermined power value (flickers to other lighting devices or the like). A relatively low power value that is assumed not to cause a phenomenon (for example, 600 W when the power value of the target power that can be used for heating the heat roller 26 is 1500 W.) In this first period, the frequency of the high-frequency current that is changed with the passage of time is set so that the decrease per unit time of the frequency of the high-frequency current is increased. Further, from the time when the value of the power supplied to the heat roller 26 reaches the predetermined power value, a predetermined target power (a power value that can be used for heating the heat roller 26. For example, 1500 W). ) Is a second period, and in this second period, the frequency of the high-frequency current is decreased per unit time so as to be smaller than the decrease of the first period. The frequency of the high-frequency current that is changed along with is set.

  The first period and the second period are measured and set in advance according to the surface temperature of the heat roller 26 and the power supply voltage value supplied to the heat roller 26.

  FIG. 4 is a graph showing the frequency change pattern of the present embodiment in comparison with a conventional frequency change pattern. As shown by a solid line in FIG. 4, the frequency change pattern of the present embodiment is set to a lower frequency at each time point until reaching the target power than the conventional frequency change pattern shown by a broken line in FIG. FIG. 4 shows a frequency change pattern used when the surface temperature t is 50 ° C. and the power supply voltage value v is 100 (V) as the frequency change pattern of this embodiment.

  FIG. 5 is a graph showing changes in electric energy when the frequency of the high-frequency current is changed according to the frequency change pattern.

  When the frequency of the high-frequency current is changed according to the frequency change pattern, the frequency change pattern of the present embodiment shown in FIG. 4 is the unit per unit time in the first period as shown by the solid line in FIG. The amount of power change is relatively large and is supplied to the heat roller 26 so that the amount of power change per unit time is relatively small in the second period, which is the amount of power assumed to cause the flicker phenomenon. A change in the amount of power is set. On the other hand, the power amount change indicated by a broken line in FIG. 5 is a case where the power change amount per unit time, which has been conventionally performed, is made constant.

  As shown in FIG. 5, if the frequency of the high-frequency current in the period from the start of supply of the high-frequency current to the arrival of the target power is changed based on the frequency change pattern of the present embodiment, the present embodiment This frequency change pattern can reach the target power at a point earlier than the conventional amount by increasing the power increase amount per unit time in the first period.

  The frequency control of the high frequency current by the IH control unit 41 during the fixing operation by the fixing device 28 will be described. FIG. 6 is a flowchart showing the frequency control of the high frequency current by the IH control unit 41 during the fixing operation by the fixing device 28.

  When receiving the fixing instruction signal from the main body side control unit 51 (YES in S1), the IH control unit 41 acquires the surface temperature t of the heat roller 26 at this time from the temperature sensor 44 (S2), and further, the heat roller 26. The power supply voltage value v supplied to is acquired from the voltage detection unit 45 (S3).

  The IH control unit 41 calculates a frequency change pattern corresponding to the acquired surface temperature t and power supply voltage value v by reading from the frequency change pattern storage unit 411 (S4).

  Then, the IH control unit 41 changes the frequency output to the drive circuit 42 based on the read frequency change pattern (S5). In other words, the IH control unit 41 starts measuring the elapsed time with the built-in timer at the start of the frequency change control (starts the supply of high-frequency current), and determines the frequency indicated by the read frequency change pattern according to the elapsed time. Output to the drive circuit 42. The drive circuit 42 supplies a high-frequency current to the excitation coil 43 at a frequency sent from the IH control unit 41. The frequency change pattern is set to be constant after the target power is reached.

  When the frequency change pattern corresponding to the acquired surface temperature t and the power supply voltage value v is not stored in the frequency change pattern storage unit 411, the IH control unit 41 (1) the acquired surface temperature t and A frequency change pattern corresponding to the surface temperature t and the power supply voltage value v that most closely approximates the power supply voltage value v is read from the frequency change pattern storage unit 411 and used, or (2) stored in the frequency change pattern storage unit 411. The frequency of the high-frequency current corresponding to each elapsed time used for the frequency change control in S5 is calculated by linear interpolation based on each frequency change pattern.

For example, when the frequency change pattern corresponding to the acquired surface temperature tx and power supply voltage value vx is not stored in the frequency change pattern storage unit 411, first, the same surface temperature t1 and different power supply voltage values v1, v2 The frequency f3 in the case of the power supply voltage value vx at the surface temperature t1 is calculated by linear interpolation represented by the following equation using two frequency change patterns corresponding to.
f1 [V = v1, T = t1, elapsed time TM = tm1] = f1 [kHz] Equation (1)
f2 [V = v2, T = t1, elapsed time TM = tm1] = f2 [kHz] ... Equation (2)
Then, the following is calculated by linear interpolation based on Equation (1) and Equation (2).
f3 [V = vx, T = t1, TM = tm1] = (vx-v1) × (f2−f1) / (v2−v1) + f1 = f3 [kHz] (3)
Subsequently, the power supply voltage value vx at the surface temperature t2 is obtained by linear interpolation shown in the following equation using two frequency change patterns corresponding to the power supply voltage values v1 and v2 having a surface temperature t2 different from the surface temperature t1. In this case, the frequency f6 is calculated.
f4 [V = v1, T = t2, elapsed time TM = tm1] = f4 [kHz] ... Equation (4)
f5 [V = v2, T = t2, elapsed time TM = tm1] = f5 [kHz] ... Equation (5)
Then, the following is calculated by linear interpolation based on Equation (4) and Equation (5).
f6 [V = vx, T = t2, TM = tm1] = (vx-v1) × (f5−f4) / (v2−v1) + f4 = f6 [kHz] (6)
The frequency f7 corresponding to the surface temperature tx and the power supply voltage value vx at the time of the elapsed time TM = tm1 (msec) is calculated by the following equation by linear interpolation based on the equations (3) and (6).
f7 [V = vx, T = tx, TM = tm1] = (tx-t1) × (f6-f3) / (t2-t1) + f3 = f7 [kHz] (7)
As described above, the IH control unit 41 determines the frequency of the high-frequency current supplied to the exciting coil 43 when the belt temperature T = tx (° C.), the power supply voltage V = vx (V), and the elapsed time TM = tm1 (msec). As described above, f7 [kHz] (equation (7)) calculated by the linear interpolation is used.
Note that linear interpolation using the respective equations is merely an example, and other calculation methods may be used.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, the configurations and processes shown in FIGS. 1 to 6 are only one embodiment of the configurations and processes of the induction heating device 10, the fixing device 28, and the image forming apparatus 1 according to the present invention, and the induction heating device according to the present invention. 10 is not intended to limit the fixing device 28 and the image forming apparatus 1 to the configuration and processing.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Induction heating apparatus 21 Image forming part 26 Heat roller 27 Pressure roller 28 Fixing apparatus 41 IH control part 411 Frequency change pattern memory | storage part 42 Drive circuit 43 Excitation coil 44 Temperature sensor 45 Voltage detection part

Claims (4)

An exciting coil for heating the heat roller by electromagnetic induction;
A current supply controller for controlling the supply of high-frequency current to the exciting coil;
From the start of the supply of the high-frequency current to the excitation coil until the value of the power supplied to the excitation coil reaches a predetermined power value that is assumed not to cause flickering in other lighting devices . In the first period, the frequency per unit time of the high-frequency current is increased and the frequency is continuously decreased, and the value of power supplied to the exciting coil reaches the predetermined power value. In the second period from the point in time until reaching a predetermined target power that can be used for heating the heat roller, the amount of decrease in the frequency of the high-frequency current per unit time is less than the amount of decrease in the first period. An induction heating apparatus comprising: a frequency changing unit that continuously reduces the frequency and lowers the frequency to change the frequency of the high-frequency current set by the current supply control unit. A voltage detection unit for detecting a power supply voltage supplied to the excitation coil;
A temperature detection unit for detecting the temperature of the heat roller ;
The frequency change unit stores a plurality of frequency change patterns indicating patterns of a decrease width of the high-frequency current frequency in the first and second periods, and is detected by the voltage detection unit immediately before the start of high-frequency current supply A frequency change pattern corresponding to the power supply voltage and the temperature of the heat roller detected by the temperature detection unit is selected from the plurality of frequency change patterns, and the current supply control unit according to the selected frequency change pattern. The induction heating apparatus according to claim 1, wherein a frequency of the set high-frequency current is changed. The induction heating device according to claim 1 or 2,
A heat roller that will be heated by the induction heating device, and a pressure roller which is brought into contact with the heat roller, a fixing for fixing the formed on a recording medium an image on the recording medium by the heat roller and the pressure roller And a fixing device. The induction heating device according to claim 1 or 2,
An image forming unit that forms an image based on image data on a recording medium;
A heat roller that will be heated by the induction heating device, and a pressure roller which is brought into contact with the heat roller, a fixing for fixing the formed on a recording medium an image on the recording medium by the heat roller and the pressure roller And an image forming apparatus.

Images